New coach Ewen McKenzie is under mounting pressure as the Wallabies attempt to avoid the ignominy of a fifth straight Test defeat against Argentina in the Rugby Championship on Saturday.

It has been a rocky start for McKenzie since he took over from Robbie Deans in July, with the Wallabies on their worst run since 2009 and edging closer to the seven Test defeats they suffered under Eddie Jones in 2005.

McKenzie has lost his first three Tests and reacted by benching Will Genia, rated one of the best scrum halves in the world and who skippered the Wallabies in their 38-12 defeat to South Africa in Brisbane last weekend.

Australia is rooted to the bottom of the Rugby Championship standings, below the Pumas, who are also winless after three games but have notched a bonus point in the struggle to avoid the wooden spoon.

South Africa and New Zealand, who meet in Auckland on Saturday, both have three victories in the four-nation southern hemisphere competition.

...there is a continued determination from the coaching staff and players to play with ambition and flair. We aren't moving away from this philosophy.

Ewen McKenzie

With Genia demoted, Brumbies' Nic White has been given his chance in Perth, starting at scrum half with number eight Ben Mowen the new captain as the coach searches for a winning combination.

With regular skipper James Horwill sidelined by injury and Genia a substitute, Mowen will lead the Wallabies in only his seventh Test appearance after making his debut in June.

McKenzie, who took the helm following Australia's defeat to the British and Irish Lions, said he has been disappointed by the team's performances but remains confident the Wallabies can turn it around by adjusting some elements of their game plan.

"We made it clear before our first game against New Zealand that this group had very strong ideas around how they wanted to approach and play each game," he said.

"Australian rugby is renowned for smart, attractive and running rugby and there is a continued determination from the coaching staff and players to play with ambition and flair. We aren't moving away from this philosophy."

The Pumas, who competed well before going down 28-13 to the All Blacks in Hamilton last weekend, loom as a danger, particularly in the forward set pieces and will be chasing only their second Test win against Australia away from home after victory in Brisbane in 1983.

Argentina head coach Santiago Phelan has made five changes from the team that lost to the All Blacks, with Tomas Cubelli to start at scrum half and 84-Test veteran Felipe Contepomi partnering London Welsh-based Gonzalo Tiesi in the centres.

Juan Imhoff has been restored to the wing and Agustin Creevy will be the hooker with Eusebio Guinazu relegated to the reserves.

Graham Henry, New Zealand's 2011 World Cup-winning coach, has been helping the Pumas this season as a consultant and Contepomi said he had given Argentina valuable insights into their rugby rivals along with tactical advice.

"He knows the Wallabies much better than we do and it's great to have his inside knowledge," Contepomi said. "He can add to our rugby culture."

The Pumas, who have not beaten the Wallabies since 1997, are bracing for an onslaught from the home side.

"Sometimes when teams are in crisis, they become stronger," Contepomi said.

"They've got great individual players and great coaches. It will soon click, but hopefully not on Saturday.

"Australia are a better team than us, and they will be after the game.

"But they need to prove it in those 80 minutes. You never know what could happen. If we could play good rugby and have a victory, it would mean a lot to us."